Field
The present disclosure relates to a power amplifier.
Description of the Related Art
As a high-efficiency power amplifier, a Doherty amplifier is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 8-330873. As disclosed in the publication, a Doherty amplifier includes a carrier amplifier and a peak amplifier connected in parallel. The carrier amplifier operates irrespective of the power level of the input signal. The peak amplifier is off when at a low power level of the input signal and operates at a high power level of the input signal. In such a Doherty amplifier, a λ/4 transmission line is commonly adopted on the output side of the carrier amplifier to change the load impedance of the carrier amplifier in accordance with the operating state of the peak amplifier.